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Том 59, № 9 (2016)
- Год: 2016
- Статей: 6
- URL: https://bakhtiniada.ru/0735-2727/issue/view/10886
Article
Estimation of the energy spectrums of reflections in pulse Doppler weather radars. Part 2. Extreme performance
Аннотация
This is the second paper in a series of papers dedicated to the peculiarities of estimation of the continuous energy spectra of random processes of different nature, which are determined by their samples at discrete moments of time. In this paper we analyze extreme performance of the reconstruction of continuous energy spectra, in particular, the ones of interperiod fluctuations of reflections from meteorological objects in pulse Doppler weather radars under the hypothetical conditions of a priori known covariance matrix of the analyzed processes. The reasons, which cause known disadvantages of classical (nonparametric) spectral estimation (SE) methods for energy spectrums shape reconstruction, are discussed. We have considered known and suggested criteria, using which the extreme performance of classical SE methods and parametric superresolution ones has been quantitatively compared. It has been demonstrated that the extreme performance of SE methods contains important but not comprehensive information. In order to choose a SE method appropriate for operation under real-world conditions, this information should be used together with information on a corresponding method’s adaptive performance under a priori unknown statistical characteristics of input effects.
379-396
Mathematical model of digital frequency-sampling filters with shiftable phase-frequency characteristic
Аннотация
The paper presents mathematical models of digital frequency-sampling filters with shiftable phase-frequency characteristic (PFC) and a generalized mathematical model taking into account the PFC shift introduced at the input. The conducted investigations made it possible to develop a class of narrow-band filters with the possibility of PFC shift and the real-time variation of instantaneous phase of the output signal.
397-401
Selection of parameters of the ferrite element for pulse UWB receiving antenna
Аннотация
Thetheoretical model of pulse ultrawideband (UWB) receiving antenna consisting of a ferrite element surrounded by a coil of conductor is investigated. The magnetodielectric cylinder of infinite length is selected as the ferrite element. The excitationUWBsignal represents a pulse of electromagnetic field with the envelope in the form of a Gaussian function with high-frequency filling signal. The peculiarities of amplitude-time dependence have been considered for the pulse of induction electromotive force occurring in the closed conducting loop, which surrounds the cylinder, under the assumption of absence of its influence on the scattered fields inside and outside the cylinder. The connection between the electromagnetic parameters of the ferrite element and the frequency-time parameters of the excitation pulse electromagnetic field, which are optimal from the point of view of effective undistorted signal reception, has been determined.
402-408
Method of image filtering using singular decomposition and the surrogate data technology
Аннотация
A method for nonlinear filtering of additive noise on digital image has been proposed. This method is based on presenting the image by its matrix singular decomposition and applying the surrogate data technology to components of the image. The proposed method ensures a superior resolution as compared to most common methods of window filtering that is corroborated by the results of simulation modeling.
409-416
Digital generation of wideband chaotic signal with the comb-shaped spectrum for communication systems based on spectral manipulation
Аннотация
An algorithm for the digital generation of broadband chaotic signal with comb-shaped spectrum has been developed on the basis of nonlinear discrete system with delay. The data transmission method using the spectral manipulation technique with digital generation and processing was experimentally implemented. The results obtained can be utilized in the systems of transmitted data security from unauthorized access.
417-422
Statistical analysis of rain height over Malaysia
Аннотация
Rain height is one of the key parameters in rain attenuation prediction. However, few studies on it had been carried out due to unavailability of data especially over tropics. Presented here is the result of eleven years zero degree isotherm height for eight locations over Malaysia. The studies had been carried out over two main seasons in the country (Northeast and Southwest Monsoon). The result shows that rain height is grossly under estimated by ITU-R P. 839-3.
423-426